Generally, in the process of acquiring seismic data, recording instruments responsive to particle motion are selectively positioned above the subterranean formation of interest. Energy, generated by artificial means, such as for example by explosives, air guns or vibrators, transmitted into the earth imparts motion to the area of the earth proximal to the origin of the seismic energy. The transmitted energy is then reflected and refracted by subsurface geological strata. Reflected and refracted energies are recorded by the receivers, such as geophones or hydrophones, responsive thereto.
For seismic exploration conducted on land or below the surface of the earth such as in a well bore, geophones are generally used to record reflected and refracted energies. For seismic exploration conducted at sea, hydrophones are generally used to record reflected and refracted energies. Whether seismic exploration occurs on land, in a well bore or at sea, both types of receivers, hydrophones and geophones, generally require signal conductors, such as electrical conductors, for interconnecting such receivers and for connecting such receivers to other recording and processing equipment.
Preferably, due to greater flexibility, resiliency, and signal portability, multi-stranded signal conductors are use for seismic exploration. An assembly of signal conductors connected to receivers (hydrophones and/or geophones) is commonly referred to as a "cable array". In many instances, the cable array may consist of a plurality of sub-cable arrays connected together, such as the Ocean Bottom Cable Assembly, a product of Halliburton Geophysical Services.
In many instances, cable arrays are deployed in austere environments. Under these conditions, cable arrays must be designed such that the components, i.e., receivers, signal conductors, and connections between the receivers and signal conductors, remain insulated from such conditions. When designing cable arrays for operation in such austere conditions, preventing the intrusion and migration of a fluid, such as water, within the cable array is a concern.
Generally, the cable array designer may select an elastomer, such as polyurethane or neoprene as a primary insulator which is placed between the receiver or signal conductors and the environment. This is done by jacketing the hydrophones and geophones and capturing the signal conductors with an overlying layer of elastomer. This layer of elastomer may be referred to as the cable array jacket. Further protection may be achieved by inclosing the jacketed cable array in metal. However, this assembly may not be suitable for certain marine applications. Additionally, individually jacketed signal conductors may also be used. In this way, the jacketed cable array may include a bundle of individually jacketed signal conductors.
It is also common, once the jacketed signal conductors are bundled and jacketed to place a fluid blocking material between the jacketed signal conductors and the cable array jacket. Traditional fluid blocking materials include depolymerized rubber, silicon, and urethane fluid. In the event the cable array jacket is opened to the environment, such as by tearing, puncturing etc., these fluid blocking materials provide additional protection from fluid intrusion and migration.
However, the inventor has discovered, notwithstanding the above described measures, fluid intrusion, particularly water intrusion via an opening in the cable array jacket can result in impaired cable array performance. Water intrusion and migration may not only degrade the performance of receivers adjacent the jacket opening but may, if the conductors within the jacketed cable array are also exposed to the environment, render the entire array or sub-array inoperative. In such circumstances, the inventor has discovered that water migration occurs not only between the cable array jacket and the signal conductors jacket but also between the signal conduit jacket and the signal conductors. Thus, there exist a need for preventing fluid intrusion and migration between the signal conductors jacket and the signal conduit.